This is how the protection of the biodiversity of a marsh allows the production of renewable energy

In order to reconcile development objectives and the protection of biodiversity, Bordeaux Métropole acquired in 2017 the Peychaud marsh in the municipality of Ambarès-et-Lagrave in Gironde. This 200-hectare site is located in Entre-Deux-Mers, in a flood zone and Natura 2000. A study carried out by the associative company Solagro shows that it is possible to produce biomass-energy in the reedbeds while preserving biodiversity.

The Marais de Peychaud is a recognized area of ​​remarkable interest from the point of view of fauna and flora. The challenge is therefore to preserve or even reinforce existing habitats such as hedges or trees favorable to biodiversity and to restore the wetland.

After having carried out a diagnosis of the territory, the study carried out by Solagro crossed the possibilities of production of plants guaranteeing the preservation of biodiversity with the possible energy outlets in the territory of the Marais. It appears that the most suitable solution for recovering the energy from the biomass produced in the Marais consists of using it in the existing wood boilers in the region.

The wood energy sector is indeed well developed in Gironde, and particularly in the Bordeaux Métropole conurbation, which has several collective boiler rooms supplying heating networks, public or private.

The willow and the reed to preserve biodiversity

At the end of the phase of diagnosis of energy outlets, several vegetable productions were imagined and it is the mixed sector of production of wood chips from willow and reeds which was retained.

The reed is a species naturally present in the immediate vicinity of the Peychaud marsh. It is a crop that adapts to the context of the marsh because it likes to have its "feet in the water" for a good part of the year, while showing excellent resilience to episodes of intense drought. It is also a habitat of choice for the nesting of many species of marsh birds.

The willow was chosen because it is a species that already spontaneously colonizes the marsh in the wettest areas. It can serve as a hedge and an agro-ecological corridor in the implementation of a crop patchwork. Planted inter-row, it will be exploited by the technique of short rotation coppice (SCR).

While the reedbeds will be mowed every year, the willow plants will be cut every seven years. The chips produced will supply the existing wood boilers in the metropolis.

An innovative sector

The study led to the formulation of an innovative sector. If it materializes in an implementation, it will be a great first because the mechanized and large-scale harvesting of reeds does not yet exist in France.